Playing it safe at early life stages: Balancing energy allocations to maximize fitness under seasonal pathogen dynamics

Juvenile amphibians are hard to monitor because of their small size, yet this is often the stage most vulnerable to disease and environmental stress. This study introduces a theoretical framework linking early-life trade-offs between growth and immune defenses to infection outcomes and individual fitness under seasonal pathogen dynamics. We parameterized the model with empirical data on growth, seasonal prey availability and Batrachochytrium dendrobatidis (Bd) infection dynamics in the tropical direct-developing coqui frog, Eleutherodactylus coqui. We identified the hatching season that minimizes long-term costs of infection for individual's growth, survival, and lifetime fecundity. Because the framework is based on species-specific life-history data, conservation practitioners can retune it to find optimal release ages and seasonal windows for other vulnerable amphibians, as well as the best timing for invasive-species control. Timing interventions to match favorable conditions should increase reintroduction success and strengthen population resilience to emerging diseases.